In insensitive artillery munitions, there is no direct contact between the insensitive high explosive (IHE) and the wall of the projectile in order to prevent the development of thermal stresses due to the different coefficients of thermal expansion of the IHE and the projectile casing. Therefore, a liner, usually a plastic bag, is placed between the two in the projectile casing. The IHE is then cast and cured.
EP 1 338 860 B1 discloses a large-caliber high-explosive projectile and a method for producing it. This document proposes a liner in the form of a plastic casing made of an elastic material, so that the changing volume of the high-explosive charge that occurs during temperature fluctuations is absorbed by the elastic plastic casing. The liner, in the form of a structure that is folded together or pressed together, is inserted through a fuse hole, which normally serves to hold the nose fuse. In its unfolded state, this bag-shaped plastic casing conforms to the dimensions of the interior of the high-explosive projectile.
In some cases, the liner is not stiff enough to be able to compensate its own thermal expansion in line with the expansion of the high-explosive charge. Due to its great thermal expansion, the high-explosive charge contracts and expands by several mm during cooling and heating, respectively. The liner contracts with the high-explosive charge but does not expand with it to the same extent. This causes a displacement of the liner on the high-explosive charge. Over many changes in temperature, the liner shifts to the rear relative to the high-explosive charge, so that the charge can become partially exposed.